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Explore Alliance Affiliate Organization - Warren Rupp Observatory - Hidden Hollow Star Party

Explore Alliance Affiliate Organization - Warren Rupp Observatory - Hidden Hollow Star Party
Mansfield, OH USA

Warren Rupp Observatory is an astronomical observatory owned and operated by Richland Astronomical Society. Built in 1985, it is located on the Friendly House Hidden Hollow Camp south of Mansfield, Ohio (USA).

The telescope is one of the world's largest amateur operated telescopes. It has public observing nights on the first Saturday of every month, weather permitting.

Warren Rupp Observatory holds public education and astronomy outreach programs regardless of weather conditions on all regularly scheduled public nights. Viewing through the 36" is only weather dependent and indoor facilities are available for programs. The Observatory is also the showpiece of the Hidden Hollow star party.


The mirror blank for the 31" telescope was donated to the Lake Erie Astronomical Project by General Electric in 1968. The blank was originally intended for use McMath Solar Observatory on Kitt Peak, Arizona, which rejected the blank in favor of a larger mirror. Approximately 2,000 subsequent hours were spent grinding the mirror. The telescope saw first light in 1974.

The telescope was donated to the Richland Astronomical Society in 1982 provided there would be a building to house it. The project was primarily financed by member Warren Rupp, after whom the observatory is named, and construction was completed in 1985. The completed telescope weighed over 7,500 pounds, and was an f/6.8 Newtonian.

The original mirror was damaged in 2011 when the telescope’s secondary mirror fell into the 31” primary and cracked it in half. The primary was promptly replaced with the current 36” f/6.3 mirror, the dimensions of which were selected to fit the existing dome and mount.

Hidden Hollow Star Party

For long time star party fans, you know the legend of Hidden Hollow as one of the friendliest and most comfortable star parties around. We’re nestled deep in the woods of Hidden Hollow resident camp in northeast Ohio near the town of Mansfield. Each year we provide some of the finest guest speakers available and they join in the fun!

Unlike other star parties, we provide cabins and bunkhouses for your comfort, as well as primitive camping, hot showers, modern restrooms and a food service vendor. If it rains? It’s no problem. We have indoor facilities and all activities go on. There’s warm areas where you can gather around a fire and converse, places to watch movies, play cards or just hang out. The observing field is well-drained and groomed with plenty of “space” to go around and, of course, you won’t want to miss the views through the Observatory’s incredible 36″ Big Blue Beast!

One of the most appealing parts about Hidden Hollow is the location itself. Even if you aren’t interested in staying up all night observing, you’ll fully appreciate the fine scenery of the camp itself. During the Fall season, Ohio offers some of the most spectacular foliage in the United States and the pristine, quiet and peaceful surroundings of Hidden Hollow are an ideal place to relax and have an enjoyable weekend. There’s plenty of trails to walk in the woods and nearby attractions, restaurants and shopping. Children and families are always welcome here!

Thanks to wide open spaces and peaceful seclusion you’ll have a wonderful time at the Hidden Hollow Star Party. Our guests have voted us #1 as one of the most beautiful astronomical retreats in the country. During your weekend stay you’ll be treated like family as you enjoy our many workshops, contests, vendors, programs, fantastic prizes and observing. We welcome visitors of all ages and you’ll find that no matter where you roam… There’s no place like our home!




  • TBA 

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